Fluid samplers



July 2, 1963 J. W. KISLING lll FLUID SAMPLERS Filed April 27, 1959' IN VEN TOR.

Bf' fm/aw ATTORNEY United States Patent O 3,5;955130 Lilli) SAMPLERSJames W. Kisling IH, Houston, Tex., assigner to Schlumberger WellSurveying Corporation, Houston, Tex., a corporation of Texas Filed Apr.27, 1959, Ser. No. 809,162 12 Claims. (Cl. 16o-163) This inventionrelates to iluid sampling apparatus and, more particularly, to samplingapparatus to obtain fluid samples representative of the fluid at a givendepth in a well bore.

Present iiuid sampling `devices now in use generally fail in some mannerto provide for the :collection and retention of ra truly representativelluid sample from a well bore. rThis is particularly true when the iiuidbeing sampled is near the two-phase equilibrium point such that a slightdisturbance will cause volumetric changes in the iluid due to theconversion of liquid to gas or vice versa. The disturbance, for example,may be due to restricted or turbulent fluid flow such that anappreciable lowering of pressure occurs during the collection of fluidwhich results in gas separation.

Another difficulty in collecting la uid sample is that the sample isoften obtained after exposure of the `sample chamber to the iluid columnduring the trip into the hole. This contamnates `the sample with fluidsfrom other regions than the one of primary interest. Still anotherdiculty is the loss or" pressure or uid from a sampler due to theinaccurate operation of valves closed by differential pressure as thetool is raised from a sampling position.

This invention overcomes the aforesaid dihculties by satisfying fourbasic conditions. First, the sample chamber is maintained at zero volumeuntil lthe time arrives to collect the sample. Second, the samplingprocess does not begin until desired and can be accomplished with thetool held stationary yat a given depth. Third, the speed of the samplegathering is controlled such that laminar liow exists and there is noturbulence; and fourth, at the conclusion of the sampling, the chamberis closed with no change in volume such that there is no tendency toalter the contents of the sample.

Accordingly, it is an object of the present invention to provide a newand improved apparatus for obtaining a sample of borehole fluid in whichthe sample will not change phase as a sample is taken.

lt is another object of the present invention to provide new andimproved apparatus for obtaining a borehole fluid sample in which thesample chamber is not exposed to well iiuids before a sample is taken.

Still mother object or" the present invention is to provide new andimproved borehole apparatus for obtaining a iluid sample.

Yet another Iobject of the present invention is to provide new andimproved apparatus in which all of the sample obtained by `a iluidsampling apparatus may be transferred under pressure to a separatecontainer.

These and other objects of the present invention are accomplished byapparatus provided with an expandable sample-receiving chamber which .isnormally maintained at zero volume until it is desired to obtain asample. To obtain a uid sample at the desired location, the chamber ispermitted to expand at a controlled rate until a predetermined volnme iscontained in the chamber. Thereafter, the fluid sample is isolated fromthe borehole iluid. More speciiical'ly, a housing contains a pair ofrelatively movable pistons, the pistons being adapted to 'oe releasablyheld in adjacency so that there is zero volume between them before afluid sample is taken. When a iluid sample is desired, one of thepistons is released for movement under the inuence of a fluid samplereceived 2 through an opening between the pistons. The one piston movesrelative to fthe other a predetermined distance thereby expanding thevolume of the chamber to la predetermined value whereupon both pistonsare movable to isolate the chamber from the sample admitting openingthus entrapping a lluid sample between the pistons.

The novel `features of the present invention are set forth withparticularity in the appended claims. The present invention, both as toits organization and manner of operation together with further objectsand advantages thereof, may best be understood by way of illustrationand example of certain `embodiments when taken in conjunction with theaccompanying drawings in which:

FIG. l is a View in cross section of 'apparatus embodying the presentinvention in one condition :of operation.

FIG. 2 is a view in cross section of apparatus embodying the presentinvention in another condition of operation.

Referring now to FIG. 1, the sampling apparatus according to the presentinvention includes a housing 1l) made up of upper and lower tubularmembers 11 `and 12 respectively connected to an intermediate cylindricalicoupling member 13, a bottom end cap 1d and an upper end cap 15. Thecap 15 is coupled to :an electricm cable 16 for suspension of theapparatus in a well. Well-known means (not shown) provided at thesurface of the `earth are employed to raise and lower the apparatus todesired levels in a borehole and the apparatus itself may belconstructed small enough for passage through tubing as Well as a casedor open holle- The lower tubular member 12 forms a cylinder 17 in whicha pair ot pistons 1S, 19 are slidably received. The piston 1S, which isdisposed between piston 19 and cap 1d, has a downwardly facing annularshoulder Ztl formed between a piston head and a portion of smallerdiameter, the shoulder 2li being adapted to abut with an upwardly facingannular shoulder 21 on the bottom end cap 14. End cap 14 also has anopening 23 to permit well lluid access to the lower side lof piston 1Swhile tubular member 12 has openings or ports 25 just above the upperside 2d of piston 13 v(in its lowcrmost position) thereby permittingpiston 1S to be pressure balanced in the described position. Projectingupwardly from the upper face of piston 18 is a smaller diametered pistonrod 27 which has its upper end 27a slidably received Within a bore 2S of'the coupling member 13. The end 27a is provided with a sealing means2712 while the bore 28 is connected by a passageway 25" to the exteriorof the coupling member for pressure balance. Intermediate the length ofrod 27 is an annullar projection 3d which forms an upper shoulderadapted to abut coupling member 13 when the rod 27 and piston 18 moveupwardly for a given distance. To lock the rod 27 and piston 19 in anuppermost position, the upper end of the rod 27 in bore ZS has anannular detent groove 31 which is adapted, when projection Sib abutsmember 13, to receive a detent 32, the detent 32 being spring mounted incoupling member 13 so as to latch with groove 31.

To provide a sample-receiving chamber portion 37a which will initiallyhave zero volume, the lower face 3 3 of `the upper piston 19 ispositioned adjacent to and in abutment with the upper face 26 of piston1S, the faces 26, 33 being substantially parallel to one another. Piston19 has a central bore 35 which receives piston rod 27, the piston 19being relatively movable between the piston 1S and abutment 3i) onpiston rod 27. Pistons 18 and 19 are provided with sealing means 34a,Slab such as O-rings `disposed above and below openings 25. Since theseal 34a of piston 19 is above openings 25 in tubular member 12, thehydrostatic pressure of fluid in the well is applied to one side ofpiston 19. The upper side 36 of piston 19 together with cylinder 1'7 andcoupling member 1,3 form another chamber portion 37 which is iilled witha relatively incompressible fluid, such as water `or oil. The fluid canbe at atmospheric pressure so that well pressure transmitted through thepistons maintains the same pressure on the fluid in chamber 37 as inwell bore. The Huid also can be placed under an initial pressure tominimize effects of compressibility, if desired or necessary. Of course,piston 19 and rod 27 as well as cylinder 17 are suitably fluid sealed,for example, by O rings 34, 34d; and, without further description, itwill be readily apparent to those skilled in the art that fluid seals,such as O rings 34, 34d are employed throughout the apparatus wherenecessary or desirable.

Chamber 37 is connected via a passageway 39 in coupling member 13 to alow regulating means 4t) and a break valve 41 which are disposed in acylindrical housing 42. Housing 42 abuts member 13 and is suitablysecured Within the lower portion of upper tubular member 11 in aconvenient well-known manner. Flow regulating means 4t) is illustratedas a flow restricting cylinder 44 having a small choke orifice 45permitting iluid communication between the passageway 39 and break valve41, the break valve 41 being connected to ow means 4) by a passageway47. Break valve 41 consists of a hollow plug member 1disposed in a bore49 so as to plug the bore. The plugged bore 49 is connected by anotherpassageway 55 in the housing 42 to a chamber 57 formed in the upperportion of the tubular member 11, the chamber 57 being at a relativelylow pressure, for example, atmospheric air pressure.

To open the plug bore 49 and permit fluid from chamber 37 -to pass intolow pressure chamber 57, a hammer pin Si) is slidablly disposed in abore 51 which is transverse to the plug bore 49. Hammer pin 50 is hollowand open at an end opposite to bore 49 so as to receive an explosivedevice 52. Explosive device 52 when ignited is adapted to impel hammerpin 50 into bore 49 and break `oli an end portion 53 4of the plug member41, the portion 53 being disposed in the path of movement of the 'hammerpin Si?. End portion S3 when broken oit' from plug member V41 opens apassage through the hollow portion of the plug. Explosive device 52 maybe any well-known explosive charge which is adapted to be exploded by aconventional igniter l(not shown), the igniter being connected by aconductor 58 to a source of power at the surface y(not shown).

In operation, the device is assembled with upper `and lower surfaces 26,33 of pistons 18, 19, respectively, in abutment and the lchamber 37filled with uid under pressure and blocked by plug 41, the fluid beingadmitted through an access port 69 in coupling member 13. The apparatusis then lowered into a Well, through tubing or casing, if present, tothe level at which a sample is desired, the positioning of the apparatusbeing accomplished by well-known means and techniques. Y

At the desired level, rthe pressure across piston 18 is pressurebalanced by the openings 23, 25 and 29 while the hydrostatic pressure onthe piston 19 -is balanced by the uid in chamber 37. The explosivedevice S2 is then operatedV so that hammer pin 5) is impelled into bore49 breaking the projection 53 of the break valve 41 and thereby openinga passage between chamber 37 and low pressure chamber 57 (see FIG. 2).At this point the hydrostatic pressure applied to one side yof piston 19forces the fluid in chamber 37 through the iiow regulating device 40into the chamber 57 which is art atmospheric pressure. The ow means 49determines the rate of fluid flow (i.e., by the size of the orifice 45,the viscosity of fluid in chamber 37 and the hydrostatic well pressure)so that turbulence in the sample-receiving chamber is avoided and thepiston 19 will therefore have a relatively slow upward motion. Theprecise rate of movement of Ilthe piston will be determined inaccordance with the pressures expected and regulated bythe flo-w means40.

The sample-receiving chamber 37a between the piston surfaces 26, 33 andcylinder 17 continues to expand until the upper piston 19 abuts theprojection 30 on the piston rod 27, the spacing of the pistons therebylimiting the expension and volume of the sample-receiving chamber to apredetermined value. Chamber S7 is sized so that when a lfull sampleIhas been obtained in the sample-receiving chamber, the pressure inchambers 37 and 57 remains less than the hydrostatic pressure of thewell Huid. Hence, the well iluid in the sample chamber continues toexert pressure on the piston 19 and both pistons will continue theirupward movement until the projection 30 on piston rod 27 abuts member13. Rod 27 locks in this upward position by virtue of deten-t 32 landdetent groove 31. Of course, while `the pistons are moving, the seal 34bin the lower piston 18 passes openings 25 thereby isolating thecollected sample between the pistons from the openings 25 so that thehydrostatic pressure on piston 18 continues movement of the pistons.

Thereafter, as the tool is raised from the well, the pistons 1S, 19remain in the locked position due to the locking of the piston rod 27 inits upper position. At the surface of the earth, the entire sample canbe recovered from the sample chamber inthe following manner. End cap 14is removed and the conventional devices to which the sample is to betransferred are connected to a valve 63 in piston 18. Valve 63 is openedwhile a pressure device (not shown) connected to port 6i? is pressuredup to move piston 19 towards piston 18 until the pistons are again in anadjacent position thus permitting transfer under pressure of the entiresample recovered.

While a particular embodiment of the present invention has been shownand described, it is apparent that changes and modiications may be madewithout departing from this invention in its broader aspects, `andtherefore the aim in the appended claims is to cover all such changesand modifications as fall within the true spirit and scope of thisinvention.

What is claimed is:

1. A borehole apparatus for obtaining fa representative Huid sample in abore hole comprising: a housing adapted for passage through a borehole,said housing having a cylindrical bore; rst and second pistons slidablyand sealingly positioned in said bore and relatively movable between acollapsed position of adjacency and an extended, spaced-apart positionto deiine therebetween a iluid sample-receiving chamber, said housinghaving a sample-admitting opening positioned to open between saidpistons in their collapsed position to admit a iluid sampletherebetween; means in said housing for contro1- ling the rate ofrelative movement between said pistons upon admission of a fluid sampletherebetween; `and means for coupling said pis-tons to one another atsaid extended position of said pistons for joint movement relative tolsaid sample-admitting opening to displace said pistons and sampletherebetween from access to said sample-admitting opening.

2. A borehole apparatus for obtaining a representative uid sample in aborehole comprising: a housing adapted for passage through a borehole,said housing having a cylindrical bore; first land second pistonsslidably and sealingly positioned in said bore and relatively movablebetween a collapsed position of adjaccncy and an extended, spaced-apartposition to deiine therebetween a iluid sample-receiving chamber, saidhousing having openings disposed above 4and below one of said pistons,one of said openings positioned to open between said pistons in theircollapsed position to admit a fluid sample therebetween;

means in 'said housing for controlling the rate of relative movementbetween said pistons upon admission of a iluid sample therebetween; andmeans for coupling said pistons to one another at said extended positionof said pistons for joint movement relative to `said sample-admittingopening to displace said pistons and sample therebetween from access tosaid sample-admitting opening.

3. A borehole apparatus for obtaining a representative uid sample in aborehole comprising: a hou-sing adapted for passage through a borehoie,said housing having a cylindrical bore; first yand second pistonsslidably and sealingly positioned in said bore and relatively movablebetween a collapsed position of adjacency and an extended, spaced-apartposition `to define therebetween ya fluid sample-receiving chamber, saidhousing having a sampleadmitting opening positioned to open between saidpistons in their collapsed position to admit a uid sample therebetween,yand one of said pistons having a bore; a piston rod secured to saidother piston and slidably and sealingly received by said bore in saidone piston; means in said housing for controlling the rate of relativemovement between said pistons upon admission of a uid sampletherebetween; `and a projection on said piston rod adapted to limitmovement of said one piston in said extended position, said pistonsbeing coupled at -said extended position by said one piston engagingsaid projection for joint movement relative to said sample-admittingopening to displace said pistons and sample therebetween from -access tosaid sample-admitting opening.

4. A 4borehole apparatus for obtaining a representative liuid sample ina borehole comprising: la housing adapted for passage through aborehole, said housing having a cylindrical bore; irst and secondpistons slidably and sealingly positioned in said bore and relativelymovable between a collapsed position of adjacency and an extended,spaced-apart position to dene therebetween a iiuid sample-receivingchamber, said housing having a sampleadmitting opening postioned to openbetween said pistons in their collapsed position to admit a uid sampletherebetween; means in said housing for controlling the yrate ofrelative movement between said pistons upon admission of a fluid sampletherebetween; means for coupling said pistons to one another at saidextended position of said pistons for joint movement relative to saidsample-admitting opening to displace said pistons and sampletherebetween from access to said sample-admitting opening; and means toreleasably lock said coupled pistons and sample therebetween in saidhousing after displacing said pistons and sample therebetween fromaccess to said sample-admitting opening.

5. A borehole apparatus for obtaining a representative uid sample in aborehole comprising: a housing adapted for passage through a borehole,said housing having a cylindrical bore; irst and second pistons slidablyand sealingly positioned `in said bore and relatively movable between acollapsed position of adjacency and an extended, spaced-apart positionto dene therebetween `a fluid sample-receiving chamber, said housinghaving openings disposed above and below one of said pistons, one ofsaid openings positioned to open between said pis-tons in theircollapsed position to admit a huid sample therebetween, and one of saidpistons having a bore; :a piston rod secu-red to said other piston andslidably and sealingly received by said bore in said one piston; meansin said housing for controlling the rate of relative movement betweensaid pistons upon admission of ya fluid sample therebetween; aprojection on said piston rod adapted to limit movement of `said onepiston in said extended position, said pistons being coupled `at `saidextended position by said one piston engaging said projection for jointmovement relative to said sample-admitting opening to displace saidpistons and smnple therebetween from access to said sample-admittingopening; and means to releasably lock said coupled pistons and sampletherebetween in said housing after displacing said pistons and sampletherebetween from access to said sample-admitting opening.

6. A borehole apparatus for obtaining a representative fluid `sample ina borehole comprising: a housing adapted for passage through a borehole,said housing having an expansible sample-receiving chamber includingfirst and second pistons relatively movable between a collapsed positionof adjacency and substantially zero volume and an extended, spaced-apartposition to contain a predetermined volume of Huid sample; means tolimit expansion of said chamber when said pistons are at said extendedposition yet permit said pistons to simultaneously move relative to saidhousing, said housing having ia sample-admitting opening communicatingbetween said chamber and the fluid to be sampled in the borehole, saidopening positioned to open between said pistons vin said collapsedposition so that hydrostatic well pressure tends to urge said pistons toseparate from one another from said collapsed position to said extendedposition; and means in said housing to hold said pistons in saidcol-lapsed position until it is desired to obtain a fluid sample landoperable to release said pistons from said collapsed position whereby auid sample of a predetermined volume may be obtained by movement of saidpistons to said extended position, said pistons in said extendedposition :and entrapped fluid sample therebetween being simultaneouslymovable in said housing to isolate said sample-receiving chamber fromsaid sample-admitting opening.

7. A borehole apparatus for obtaining a representative iluid sample in aborehole comprising: a housing adapted for passage through a borehole,said housing having a tubular section with la shouldered portion at oneend thereof; iirst and second pistons slidably land sealingly receivedinitially at said one end of said tubular section, said pistons beingpositioned in a collapsed position at said `one end of said section withfacing surfaces in proxirnate contact to form an expansi-blesample-receiving chamber initially at substantially zer-o volume, saidpistons being relatively movable in said tubular section to an extendedspaced-apart position thereby to expand the volume of saidsample-receiving chamber to contain a predetermined volume of iiuidsample, said housing having openings above and below one of saidpistons, said openings communicating between said tubular section andthe fluid to be sampled in the borehole, one of said openings positionedto open between said pistons in said collapsed position to permit theintroduction of hydrostatic well pressure therebetween which tends tourge the other of said pistons `from said collapsed position to saidextende-d position, and said other piston having a bore; a piston rodsecured to said one piston and slidably `and sealingly received by saidbore, said rod having a projection thereon to limit movement of saidother piston and thereby limit expansion of lsaid sample-receivingchamber when said pistons are at said extended position; and means insaid housing to hold said pistons in said collapsed position until it isdesired to obtain a fluid sample and operable to release said pistonsfrom said collapsed position whereby a fluid sample of a predeterminedvolume may lbe obtained by movement of said other piston to saidextended position, said pistons in said extended position and enrtrappedfluid sample therebetween being simultaneously movable in said tubularsection to isolate said samplereceiving chamber from saidsample-admitting opening.

8. A borehole apparatus for obtaining a representative huid sample in `aborehole comprising: a housing adapted for passage through a borehole,said housing having a tubular section with ashouldered portion at oneend thereof; first and second pistons slidably and sealingly receivedinitially at one end of `said tubular section, said pistons beingpositioned in a collapsed position at said one end of said section withfacing surfaces in proximate contact to form a iirst expansiblesample-receiving chamber initially at substantially zero volume, one ofsaid pistons having a remaining surface forming with said tubularsection a second chamber, said pistons being relatively movable in saidtubular section to an extended, spaced-apart position thereby to expandthe volume of said sample-receiving chamber to contain a predeterminedvolume of fluid sample, said housing having a sample-admitting openingcommunicating between said sample-receiving chamber and the uid to besampled in the bore hole, said opening being disposed adjacent to saidpistons in said collapsed position to permit the introduction ofhydrostatic well pressure therebetween which tends to urge said onepiston from said collapsed position to said extended position; and meansin said housing to hold said pistons in said collapsed position until itis desired to obtain a iluid sample, said holding means including arelatively incompressible fluid in said second chamber to maintain saidpistons in a position of adjacency, a third low pressure chamber in saidhousing, and means connecting said second chamber with said thirdchamber including a normally-closed valve means, said valve means, whenopen, releasing said huid in said second chamber to said third chamberthereby releasing said pistons from said collapsed position whereby afluid sample of a predetermined volume may be obtained by movement ofsaid one piston to said extended position, said pistons in said extendedposition and entrapped ilud sample therebetween being simultaneouslymovable in said tubular section to isolate said sample-receiving chamberfrom said sample-admitting opening; means in said housing for openingsaid valve means.

9. A borehole apparatus for obtaining a representative uid sample in aborehole comprising: a housing adapted for passage through a borehole,said housing having a tubular section with a shouldered portion at oneend thereof; rst and second pistons slidably and sealingly receivedinitially at one end of said tubular section, said pistonsbeingpositioned in a collapsed position at said one end of said sectionwith facing surfaces in proximate contact to form a first expansiblesample-receiving chamber initially at substantially zero volume, one ofsaid pistons having ay remaining surface forming'with said tubularsection a second chamber, said pistons being relatively movable in saidtubular section to an extended, spaced-apart posit-ion thereby to expandthe volume of said sample-receiving chamber Ito contain a predeterminedvolume of fluid sample, said housing having openings above and below theother of said pistons, said openings communicating between said tubularsection and the uid to be sampled in the borehole, one of said openingspositioned to yopen between said pistons in said collapsed position topermit the introduction of hydrostatic well pressure therebetween whichtends to urge said one piston `from saidrcollapsed position to saidextended position, and said one piston having a bore; a piston rodsecured to said other piston and slidably and sealingly received by saidbore, said rod having a projection thereon to limit movement of said onepiston and thereby limit expansion of said sample-receiving chamber whensaid pistons are at said extended position; means in said housing tohold said pistons in said collapsed position until it is desired toobtain a fluid sample, said holding means including a relativelyincompressible fluid in said second chamber to maintain said pistons ina position of adjacency, a third low pressure chamber in said housing,and means connecting said second chamber with said third chamberincluding a normally-closed valve means, said valve means, when open,releasing said fluid in said second chamber to said thirdrchamberthereby releasing said pistons from said collapsed position whereby atluid sample of a predetermined volume may be obtained by movement ofsaid one piston to said extended position, said pistons in said extendedposition and entrapped iluid sample therebetween being simultaneouslymovable in said tubular section to isolate said sample-receiving chamberfrom said vsample-admitting opening; means inV said housing for openingsaid valve means and means to releasably lock said pistons in saidhousingV after isolating said sample-receiving chamber from saidsample-admitting opening.

' l0. A borehole apparatus for obtaining a representative fluid samplein a borehole comprising: a housing adapted for passage through aborehole, said housing aosass having first and second chambers; a memberseparating said first chamber into said first and second chamberportions and adapted to move between a position in said housing wheresaid iirst chamber portion is at zero volume and a position wherein saidiirst chamber portion is at a predetermined volume, said housing havingnormally open ports to permit well iiuid access to said rst chamberportion; a relatively incompressible fluid in said second chamberportion; a passageway interconnecting said second chamber portion andsaid second chamber; and means in said passageway for releasablyblocking said passageway, said iluid in said second chamber portionserving to maintain said irst chamber portion at zero volume until saidpassageway is unblocked whereupon said iluid may be displaced from saidsecond chamber portion to said second chamber through said passageway assaid first chamber portion expands due to receipt of a fluid sample.

ll. A borehole apparatus for obtaining a prepresentative iluid sample ina borehole comprising: a housing adapted for passage through a borehole,said housing having rst and second chambers; a member separating saidrst chamber into rst and second chamber portions and adapted to movebetween a position in said housing where said first chamber portion isat Zero volume and a position wherein said first chamber portion is at apredetermined volume, said housing having normally open ports to permitwell uid access to said first chamber portion; a relativelyincompressible fluid in said second chamber portion; a passagewayinterconnecting said second chamber portion and said second chamber;means in said passageway for regulating the flow of fluid through saidpassageway; and means in said passageway for releasably blocking saidpassageway, said iluid in said second chamber portion serving tomaintain said iirst chamber portion at zero volume until said passagewayis unblocked whereupon said fluid may be displaced from said secondcharnber portion to said second chamber through said passageway as saidrst chamber portion expands due to receipt of a uid sample.

12. A borehole apparatus for obtaining a representative iluid sample ina borehole comprising: a housing adapted for passage through a borehole,said housing having first and second chambers; a pair of pistonsslidably received in said housing, said first chamber portion beingdefined between said pistons, said pistons being relatively movablebetween a collapsed position of adjacency where said rst chamber portionis at zero volume and a position where said rst chamber portion is at apredetermined volume, said housing having normally open ports to permitwell fluid access to said rst chamber portion, and one of said pistonsseparating said first chamber pontion from said second chamber portion;relatively incompressible uid in said second chamber portion; apassageway interconnecting said second chamber portion and said secondchamber; and means in said passageway for releasably blocking saidpassageway, said uid in said second chamber portion serving to maintainsaid rst chamber portion at zero volume until said passageway isunblocked whereupon said fluid may be displaced from said second chamberportion to said second chamber through said passageway as said firstchamber portion expands due to receipt of a uid sample.

References Cited in the iile of this patent UNITED STATES PATENTS Re.24,352 Comstock Aug. 27, 1957 2,201,447 Mullins May 2l, 1940 2,308,387Potts Jan. 12, 1943 2,637,400 Brown et al May 5, 1953 2,674,313 ChambersApr. 6, 1954

1. A BOREHOLE APPARATUS FOR OBTAINING A REPRESENTATIVE FLUID SAMPLE IN ABORE HOLE COMPRISING: A HOUSING ADAPTED FOR PASSAGE THROUGH A BOREHOLE,SAID HOUSING HAVING A CYLINDRICAL BORE; FIRST AND SECOND PISTONSSLIDABLY AND SEALINGLY POSITIONED IN SAID BORE AND RELATIVELY MOVABLEBETWEEN A COLLAPSED POSITION OF ADJACENCY AND AN EXTENDED, SPACED-APARTPOSITION TO DIFINE THEREBETWEEN A FLUID SAMPLE-RECEIVING CHAMBER, SAIDHOUSING HAVING A SAMPLE-ADMITTING OPENING POSITIONED TO OPEN BETWEENSAID PISTONS IN THEIR COLLAPSED POSITION TO ADMIT A FLUID SAMPLETHEREBETWEEN; MEANS IN SAID HOUSING FOR CONTROLLING THE RATE OF RELATIVEMOVEMENT BETWEEN SAID PISTONS UPON ADMISSION OF A FLUID SAMPLETHEREBETWEEN; AND MEANS FOR COUPLING SAID PISTONS TO ONE ANOTHER AT SAIDEXTENDED POSITION OF SAID PISTONS FOR JOINT MOVEMENT RELATIVE TO SAIDSAMPLE-ADMITTING OPENING TO DISPLACE SAID PISTONS AND